Image presentation method and arrangement

ABSTRACT

A method of presenting a complete image on the retina of an observer, wherein the image is comprised of a large number of pixels located along mutually adjacent lines. The presentation is effected by deflecting a limited number of pixels shown on a display over the image-perceiving area of a retina, wherein these pixels represent consecutively all pixels in the image. According to the invention, the display shows the pixels in at least one band of a limited number of complete lines in the image. The lines in the band are generated parallel with one another and such that each line represents successively the pixels in all lines of the image or a part-image. The band is deflected as a unit over the image-perceiving area of the retina in time with the generation of the lines on the display. The invention also relates to a system for use when carrying out the method.

The present invention relates to a method of presenting to the retina ofan observer a complete image comprised of a large number of pixels,located along mutually adjacent lines, by deflecting a limited number ofpixels shown on a display over the image-perceiving area of the retinaof the observer, these pixels consecutively representing all pixels inthe image. By image-perceiving area is meant the area of the retinawhich sees the image display. The invention also relates to an systemfor use when carrying out the method.

Our Swedish Patent Specification No. 9101778-0 describes a system whichcan be used to present images with the aid of this principle, amongother things. The patent specification describes generally a system forpresenting an image on the basis of at least two variables for eachpixel, such as pixel position and pixel information. The image is thuscomprised of a plurality or pixels, each defined by a pixel positiongiven by two angular coordinates in relation to a reference directionfrom the observer, and by information relating to each pixel with regardto intensity, color, polarization, etc., at each moment in time.

The novel principle disclosed in the aforesaid patent specificationenables the image presentation system, or display, to be divided intotwo parts, more specifically a first display device located at adistance from the observer, and a second display device located in thefield of view between the observer and the first display device. It isalso necessary for the presentation system to include means for mutuallysynchronizing the first and the second display devices.

According to the aforesaid patent specification, when imaging with theaid of two mutually separate display devices, these devices can beprovided with different combinations of the three variablesX-coordinate, Y-coordinate and pixel information, such as intensity,color, polarization, etc. A total of six combinations are possible fordividing these variables between the two display devices.

Our coterminous Swedish Patent Application No. 9503503-6 describessimplifications to the equipment required with some of thesecombinations, particularly those combinations in which the displaydevice which is located at a distance from the observer is provided withinformation relating to the X-coordinate of respective pixels, with orwithout pixel information. This display device will thus display a linewhich consecutively shows the pixels in all lines of the image orpicture. The line may be oriented in desired directions and be comprisedof uniformly illuminated pixels or pixels that contain informationrelating to intensity, color, polarization, etc. This display can thusbe a so-called line display.

The second display is suitably carried by the observer in the form ofspectacles (goggles) through which the line display can be viewed, andit is necessary to provide the second display device with means fordeflecting the observed or viewed line in the other direction, which issuitably perpendicular to the propagation of the line, so as to obtain acomplete image on the retina of the observer. It is thus only on theretina that the image exists in its entirety as a mean value formulationover a maximum time period corresponding to the slowness or integrationtime of the eye.

The luminance of the obtained image may constitute a limitation of thistechnique. Another limitation is that when showing only one single lineon the display, it is not possible to display directly readableinformation on this line, i.e. without the assistance of furtherauxiliaries.

The main object of the present invention is to provide an imagedisplaying method and an image display system in accordance with theaforegoing with which those limitations that are incurred when only onesingle line is deflected are eliminated, among other things.

The invention is based on the realization that this object can beachieved when instead of deflecting an individual line there aresimultaneously deflected a band of lines which lines are generated inparallel on a display such that each of these lines successivelyrepresents all lines of an image or of a part-image. The image thus“rolls” through the band synchronously with deflection of the band inthe opposite direction. The band will therewith “paint” the image overthe retina of the observer.

Each line in the image will be activated the same number of times as thenumber of lines included in the band, therewith increasing luminance bya corresponding factor.

Another advantage afforded by the use a band of lines is that certainpixels in the band can be used to present on the display, informationthat can be read directly by an observer without the assistance ofauxiliary means.

Accordingly, a method of the kind defined in the first paragraph is, inaccordance with the invention, mainly characterized in that the displayshows the pixels in at least one band of a limited number of completelines in the image; in that the lines in the band are generated inparallel simultaneously, such that each line represents successively thepixels in all lines of the image or of a part-image; and in that theband is deflected as a unit over the image-perceiving area of the retinasynchronously with the generation of the lines on the display.

This technique can be used in the construction of simpler displayscreens, for instance. Thus, the technique enables present-day displayscreens which correspond to all lines in the image to be limited to adisplay screen which shows only a few lines and supplement the screenwith a pair of spectacles worn by the observer, for instance. This canprovide many advantages in those cases where there is insufficient roomfor a full scale screen.

Remaining features of the aforedefined method and of a system forcarrying out the method will be apparent from the following.

The invention will now be described in more detail with reference to anexemplifying embodiment thereof and also with reference to theaccompanying drawings, in which

FIG. 1 is a schematic illustration of an inventive system which includesa band display and a deflecting device in the form of amirror-periscope;

FIG. 2 illustrates the principle of a band display according to FIG. 1;and

FIGS. 3A-B illustrate the modus operandi of the invention.

Shown in FIG. 1 is a band display 1, by which is meant a display thatshows one or more bands of preferably closely adjacent lines in animage. Each band may include 3-60 lines, for instance, preferably 5-25lines. The complete image may be based on a standard 625-line format,for instance, although other formats are also conceivable.

With the intention of simplifying the illustration of the presentinvention and its working principles, there is shown a three-line banddisplay which presents an image that consists of only five lines.

The reference numeral 2 identifies the light rays from three linesdisplayed on the display 1. This three-line band is deflected as a unitby a deflecting device in the form of a mirror-periscope which includesa fixed mirror 3 and an oscillating mirror 4. Two such mirror-periscopesmay be carried, for instance, by the observer in the form of a pair ofspectacles or goggles. The spectacles will deflect the lines representedby the rays 2 on the display vertically over the retina of the eye 5.The deflecting movement of the mirror is suitably represented by acyclic oscillatory movement of sinusoidal, triangular or linear rampconfiguration. When employing non-linear sinusoidal oscillation, thedistortion of the image caused by linear deflection can be compensatedfor in the manner described in our aforementioned co-terminus SwedishPatent Application No. 9503503-6.

As illustrated schematically in FIG. 2, all lines of the image or of apart-image “roll” through the display 1 when practicing the presentinvention. “Rolling” can be compared with the effect observed on aTV-set when picture syncronization is lost, giving the impression thatthe picture rolls across the TV-screen.

In the illustrated example, the display is constructed to show three ofthe image lines simultaneously. The lines are generated in parallel withone another, which can be achieved by delivering the image informationof the three lines relevant at each point in time to the display 1 inparallel, ie simultaneously, from a shift register 6. As an alternativeto a display operated by three electron beams, the display may comprisea display in which each pixel is comprised of a light-emitting diode orlike device, for instance. The pixels in respective lines may therewithbe activated in parallel instead of sequentially.

The band of lines presented on the display 1 is deflected with the aidof the deflecting mirror 4 in FIG. 1 synchronously with the generationof the lines, but in a direction opposite to the “rolling movement” onthe display. To the observer it will appear that the rolling movementhas stopped, although the displayed image actually still continues toroll. As a result, an image containing the full number of lines is“painted” over the observer's retina during one-half period of theoscillatory movement of the mirror. Possibly, only one so-calledhalf-image can be created in interlace format during each half period.

A flutter-free image can be obtained when at least one image field isshown during the eye's integration time, which is normally from 10-20msec. In this regard, the term image also includes, for instance, apart-image and the like included in a mosaic image.

The principle of the invention will now be explained in more detail withreference to FIGS. 3A-B.

FIG. 3A is a schematic illustration of a band display at four differenttime points a)-d). The display has three line positions A, B, C forsimultaneous showing of three lines of an image as the image rollsthrough the display, which image includes only five lines in theillustrated case.

FIG. 3B illustrates the manner in which a corresponding image is paintedover the image-perceiving area of the observer's retina.

At time point a), the display shows the lines 1, 2, 3 of the completeimage, these lines being reproduced in corresponding positions on theretina, through the medium of the deflecting mirror 4 shown in FIG. 1.At the next time point b), the display shows the lines 2, 3, 4, as line1 has disappeared from the display, and the mirror 4 which swingssynchronously with the line generating process has deflected the band oflines shown on the display so that these lines will appear in correctpositions on the retina, see the corresponding part-image in FIG. 3B.

Similarly, at the next time point c) the line 2 is no longer seen on thedisplay whereas the line 5 appears for the first time. At time point d),the band of lines begins to disappear from the retina and after afurther two steps is prepared to re-enter the image field from belowsubsequent to a return sweep of the mirror 4 shown in FIG. 1. The imageis “painted” up on the retina in this way.

As will be evident from this simplified model, as each complete image orpart-image is produced, each line, see for instance lines 3 and 4, willbe activated three times, i.e. the same number of times as there arelines on the band display. Consequently, luminance is tripled incomparison with the case when only one line is deflected. The more linescontained by the band, the stronger the luminance.

The aforedescribed principle thus enables the use of a display with onlya few lines and nevertheless produce a complete image of high luminanceon the observer's retina.

The invention also affords the advantage that when the display includesthe requisite number of lines, it can also be used to presentinformation that can be interpreted without the assistance of auxiliarydevices in the form of deflecting means. This is achieved by using agiven number of pixels on the display for such information. The displaycan herewith serve two different purposes.

As an alternative to one band of lines, the display may be designed topresent simultaneously two or more separate bands either at intervals orwithout intervals. This requires parallel and synchronized feeding ofimage information to different parts of the display.

A band of lines can also be deflected with the aid of both flanks of asinusoidal oscillatory movement of the mirror for instance. In thiscase, it is necessary to read the information for the pixels in thelines in different directions during the two parts of an oscillatingperiod. Alternatively, the two flanks may be used to deliver differentinformation to both eyes of an observer, thereby enabling a stereoscopicimage to be presented to the observer. Triggering of the display linesat desired time points can be achieved readily with the aid of drivecircuits known to the person skilled in this art.

The invention has been described in the aforegoing with reference to aband of lines written in the X-direction. The principle is the same,however, irrespective of the direction in which the lines are written,provided that the deflecting means deflects the band in a seconddirection, normally a direction which is perpendicular to the firstdirection. Thus, the display can show, for instance, a band of verticallines which is propagated horizontally by the mirror over theimage-perceiving area of the retina. The first display device may alsobe provided with information concerning the Y-coordinate of respectivepixels, wherein deflection in the X-direction takes place in the displaydevice in the immediate proximity of the observer.

As before mentioned, the deflecting means can be convenientlyincorporated in a pair of spectacles. Naturally, if desired, only asingle deflecting means may be used for both eyes and incorporated in acyclops-like system. Alternatively, the system may have the form of amonocle.

As an alternative to the aforedescribed mirror-periscope, deflectionmay, of course, be achieved with the aid of any other suitableopto-mechanical device that describes a suitable oscillatory movement.Furthermore, electro-optical modulators may also be used, for instance.The sinusoidal oscillation referred to in the example may be replacedwith another harmonic oscillation, or a combination of such oscillationsmay be employed.

What is claimed is:
 1. A method of presenting a complete image on aretina of an observer, comprising: showing pixels in at least one bandof a limited number of complete lines in an image on a display;generating the lines in the at least one band in parallel with oneanother such that each of the lines successively represents the pixelsin all lines of the image or all lines of a part-image; and deflectingthe at least one band as a unit over the image-perceiving area of theretina synchronously with the generation of the lines on the display,wherein the pixels shown on the display consecutively represent thepixels in the image.
 2. A method according to claim 1, wherein thedisplay shows at least one band having three to sixty lines.
 3. A methodaccording to claim 1, wherein the display shows at least one band havingfive to twenty-five lines.
 4. A method according to claim 1, wherein thedisplay shows several bands of mutually adjacent lines.
 5. A methodaccording to claim 1, further comprising: using the pixels in the bandof lines shown on the display for directly readable information.
 6. Amethod according to claim 1, wherein the deflecting step comprises:deflecting the band with a cyclic oscillatory movement of sinusoidalform, triangular form, or linear ramp form; and utilizing the cyclicoscillatory movement for two active deflecting movements of the bandwith each cycle in mutually opposite directions.
 7. A method accordingto claim 6, wherein the band is deflected during one-half of the cycleto one eye of an observer, and is deflected during the other half of thecycle to the other eye of the observer.
 8. A method according to claim1, wherein the deflecting step comprises deflecting the band with atleast one oscillating mirror for each eye, the oscillating mirrors beingprovided within spectacles through which the display can be observed. 9.A system for presenting a complete image on the retina of an observer,comprising: a display for showing pixels in at least one band of alimited number of complete lines in an image; means for generating thelines in the at least one band in parallel with one another such thateach of the lines successively represents the pixels in all lines of theimage or all lines of a part-image; and means for deflecting the atleast one band as a unit over the image-perceiving area of the retinasynchronously with the generation of the lines on the display, whereinthe pixels shown on the display consecutively represent the pixels inthe image.
 10. A system according to claim 9, wherein the displaysimultaneously shows three to sixty lines.
 11. A system according toclaim 9, wherein the display simultaneously shows five to twenty-fivelines.
 12. A system according to claim 9, further comprising means foraddressing certain pixels in the band shown on the display withinformation that can be read directly.
 13. A system according to claims9, wherein the deflecting means comprises at least one oscillatingmirror.
 14. A system according to claim 9, wherein the deflecting meanscomprises a pair of spectacles through which the display can beobserved.